This invention relates to desiccant cartridges for use in air or fluid dryers of automotive air conditioning systems.
Desiccants are commonly used in automotive air conditioning systems for dehydrating air and refrigerants. Desiccant particles are common in such systems because the high surface area-to-volume ratios of the particles facilitates their interaction with surrounding air or fluid. Since the desiccant particles must be held in the air or fluid stream and prevented from contaminating other parts of the system, the particles must be held in a container which is permeable to the air or fluid but impermeable to the particles.
One form of dryer used in automotive air conditioning systems includes an elongated receiver or accumulator canister having inlet and outlet ports communicating with the interior of the canister. A desiccant container is positioned in the interior of the canister and allows for air and/or fluid through the desiccant material.
One form of package-type desiccant container for use in an accumulator or receiver dryer is constructed from synthetic felted wool or polyester which is filled with desiccant and then sealed by stitching or fusing. One drawback to this form of package is that the felted bag may not conform to the shape of the canister, so that air or fluid may bypass the desiccant. Another drawback is that the bag may be non-uniform in shape, thereby making automatic assembly of the dryer difficult.
If felted polyester is used as a less expensive substitute for felted wool, the seams of the bag may be formed by ultrasonic welding. Unfortunately, the reliability of such ultrasonic welds is questionable and the bag may open up, allowing adsorbent material to escape from the bag and potentially contaminate the system. In addition, the felted polyester bag is vulnerable to burn-through when the dryer is welded shut.
In another proposed form of an accumulator or receiver dryer, desiccant particles are trapped between a pair of grids or plates which are welded or press fit inside the canister. According to one embodiment, the desiccant is charged by pouring the desiccant particles into the canister once a first of the grids or plates is positioned. A pipe extends through holes in the grids or plates to exhaust dried air to an outlet port.
A dryer of this form is likely to be difficult to assemble because the grids or plates must be slid into position and, in some cases, welded inside the canister. Further, since the desiccant particles are manually poured into the container, the desiccant must be pre-measured due to the difficulty of controlling the amount of desiccant poured into the canister based on visual observation alone. The pouring of the desiccant creates a risk of accidental contamination outside the accumulator since desiccant particles may fall into the pipe communicating with the outlet port. Nevertheless, the amount of desiccant poured into the canister may vary from canister to canister for at least the reasons mentioned above.
U.S. Pat. No. 5,522,204, the contents of which are hereby incorporated by reference, discloses a desiccant cartridge which can be inserted within an accumulator or receiver dryer. The desiccant cartridge includes a cup for holding particulate desiccant and a cap which is locked to the cup by an integral detent on an inner wall portion of the cup.
U.S. Pat. No. 5,529,203, the contents of which are hereby incorporated by reference, also discloses a desiccant cartridge which can be inserted within an accumulator or receiver dryer. The desiccant cartridge includes a cup for holding particulate desiccant and a cap. The cap is designed for receipt in the chamber to cover the opening. In addition, the cap has a hole for receiving the inner wall portion of the cup. The cup includes a number of nib segments which are arranged into axially spaced nib groupings. The cap includes an edge portion which permits the cap to be retained between axially adjacent nib groupings thus retaining the cap within the cup in one of a number of axially spaced positions.
The desiccant particles are either poured directly into the cup, or into a felted bag which in turn is inserted into the cup before the desiccant cartridge is inserted within the receiver dryer. It is important that desiccant not shift once the cap is locked into place. If there is not enough desiccant to fill the predetermined volume, or if the desiccant should settle over time, then the desiccant within the container will undesirably shift within the chamber.
It has become increasingly popular and effective to place leak detection dyes in desiccant packages so that leaks in the air conditioning system can be readily identified. These dyes can be adsorbed into a host wafer of a substrate material, take the form of a powder or as a solid pellet, and such and are placed directly into the desiccant package during assembly. During operation of the air conditioning system, the dye mixes and circulates with the refrigerant which will be carried outside if there is a leak. These dyes illuminate under long wave ultra-violet light, as such, the leak in an air conditioning system can be located when long wave ultra-violet light is used. One popular leak detection dye is a fluorescent alkyl substituted perylene dye that dissolves in the refrigerant and flows through the refrigeration system as disclosed in U.S. Pat. No. 5,650,563. The contents of which are hereby incorporated by reference herein.
In these desiccant packages, when dye impregnated wafers, pellets, or the like, are inserted to provide for the desired leak detection requirements, the dye can migrate throughout the package contaminating almost all of the desiccant particles.
This dye migration does not normally interfere with the proper functioning of the desiccant. However, auto and truck manufacturers often perform loss on ignition (LOI) tests on the desiccant to assess the amount of moisture retention therein. This moisture amount is determined by the weight difference obtained before and after drying a desiccant sample at a specified temperature and for a specified period of time to achieve a constant weight. The difference in weight, calculated as a percentage of the sample""s initial weight, after being dried, is reported as LOI.
The problem is that when the dye migrates throughout a package or container, contaminating a substantial quantity of the desiccant particles, virtually no particles or an insufficient number of same are left so that accurate LOI testing can be conducted thereon. As such, dye from a dye wafer that has contaminated the desiccant particles results in false LOI readings since the analytical equipment utilized will regard the dye as being water.
Accordingly, there is a need in the art to provide a desiccant cartridge which is simple to assemble with means for retaining a cap such that the cartridge can house both desiccant particles and a leak detection dye wafer, or the like,wherein the cap prevents the dye wafer from shifting and contaminating an excessive quantity of the desiccant particles.
These drawbacks and others are overcome by means of the present invention embodied in a desiccant containing cartridge.
The desiccant cartridge includes a cup extending along an axis and having spaced inner and outer wall portions connected by a transverse portion to define a chamber having an opening for the placement of a dye wafer and desiccant particles, and a cap for receipt in the chamber. The cap has a planar portion having an outer circumference and an inner circumference defining an aperture for receiving the inner wall portion of the container when the cap is received in the chamber.
Both the transverse portion and the cap are perforated to allow air or fluid to reach the desiccant housed thereon. The outer wall portion of the cup also may include a plurality of outer wall protrusions including, but not limited to, ribs, nibs, beads, bumps or other equivalent protrusions projecting radially inwardly from the outer wall portion which engage and retain the cap in one of a number of axially spaced positions to prevent shifting of the particulate desiccant and the dye wafer within the chamber. The inner wall portion also may include a plurality of inner wall protrusions to help retain the cap. Preferably, the inner and outer wall protrusions are arranged in axially-spaced circumferential groupings.
By reason of the ability of the cap to be adjusted to a position that prevents shifting of the dye barrier and desiccant, a substantial portion of the desiccant material is not coated with the dye and thereby these uncoated particles may be removed from the cartridge and satisfactory LOI testing conducted thereon.
A preferred embodiment of the desiccant cartridge consists of a cup extending along an axis and having spaced inner and outer wall portions connected by a transverse portion to define a chamber having an opening for the placement of a dye wafer and desiccant particles, and a cap consisting of a planar portion having an outer circumference and an inner circumference defining an aperture for receiving the inner wall portion when the cap is received in the chamber. The cap further is provided with a peripheral flanged portion extending transversely from the outer circumference of the planar portion. The peripheral flanged portion having spaced apart locking tabs each with an edge portion that is adapted to fit contiguously with the outer wall portion of the cartridge.
As such, it is one object of the invention to provide a desiccant cartridge which is simple to assemble, and allows for the user to compress the cap into the cup to sufficiently eliminate empty space within the chamber.
It is another object of the invention to prevent the shifting of the dye wafer and desiccant particles, thus, eliminating attrition of the desiccant and allowing satisfactory LOI testing to be conducted thereon.
This invention also eliminates the need for external springs or other devices that add more cost to the cartridge.
Lastly, since the cup-shaped cartridge is formed into a specific, definite shape and dimension depending on the particular canister in which it is to be housed, the air or refrigerant system is efficient, minimizing by-pass of the fluid flow from the desiccant particles which can in some cases occur.
The invention will be further described in conjunction with the appended drawings and following detailed description.